(1) Field of the Invention
The invention relates to maintenance steps on helicopter fuselage according to the preamble of claim 1, a method for mounting of such maintenance steps according to the preamble of claim 9 and a method for dismounting of such maintenance steps according to the preamble of claim 13.
(2) Description of Related Art
Maintenance steps are present on principally all helicopters, for example in different numbers such as 3 per side for EC135, 3 per side for EC145 or more for NH90. Maintenance steps are used to allow the maintenance crew to get in a position where they can fulfil their maintenance tasks, especially for checks at the engines and main gear box. Maintenance steps are always located outside the helicopters, namely in the lateral shell of the helicopters. Those steps are in general part of the fuselage, but when flying they are hidden and retracted.
US 2009078827 A1 discloses a foldable step unit for a rotorcraft, the step unit being provided with a bottom step and a stationary support that is secured to the structure of the rotorcraft. The step unit comprises a left side beam and a right beam hinged on said stationary support, said bottom step being arranged on a left free end and a right free end respectively of the left and right side beams via a pivot pin, drive means for said step unit are connected via at least one control means to at least one side beam and enable said step unit to be retracted into and extended from a housing formed in the rotorcraft. This state of the art discloses a foldable step for a helicopter, but not used for maintenance but rather for passengers to enter or exit the aircraft with corresponding high demands as to safety, subsequent high complexity and thus increases maintenance needs. As well the steps or stairs disclosed in U.S. Pat. No. 2,494,367, U.S. Pat. No. 2,647,677 or U.S. Pat. No. 2,990,148 are all dedicated to give access to the inside of an aircraft and are therefore subject to different concepts of safety and operation than a maintenance step.
DE 102007022279 A1 discloses a vehicle chassis which surrounds an auxiliary equipment compartment. A step recess forms a section of the boundary of the auxiliary equipment compartment. To simplify the service and maintenance of the industrial truck, the step recess has a service and maintenance opening which can be closed by a service and maintenance cover, through which opening the auxiliary equipment compartment can be accessed. A step recess is not appropriate for an aircraft with its need of a smooth outside profile of the fuselage.
A general trend in aerospace is to reduce the direct maintenance costs. This can be done for helicopters by giving easy access from outside to all maintenance related components. A disadvantage of known maintenance steps of helicopters is that they can only be installed or replaced where access from inside is possible. Consequently the maintenance steps of the state of the art are hardly removable and in any case only from inside the helicopter, e.g. an access from inside to the bearing sleeves or bearing pins of the maintenance step is necessary for exchange of a maintenance step, i.e. it is mandatory to remove the internal carpeting. Sometimes the exchange is even impossible without removing a whole part of the fuselage. Supplemental to reduced direct maintenance costs the requests from electric installation design of the EC135 have as a consequence the request, to reduce the size of the maintenance steps in order to have more free space for harness installation inside the helicopter fuselage.